to make RBCs
1. Support (ex. to stand up)
2. Protection (ex. cover vital organs)
3. Movement - muscles covers - movement
4. Mineral storage - calcium, 98% of calcium is stored in bone. (too much calc. in blood, then store in bones - like a bank, can add to bank until 30-35)
5. Hematopoiesis (blood formation) - formation of blood cells, RBC, WBC, Platelets
can't live w/o calc.